This program is aimed at the development and application of in vivo NMR spectroscopic methods for studying metabolism and its perturbation by chemical toxins. Recent efforts in this area have focused on the analysis of the metabolism of fluorinated compounds and on the use of fluorinated compounds to probe cellular function. Determination of the structure of metabolites of fluorinated compounds by NMR presents a fundamental problem: the 19F NMR spectra typically involve only one or a few resonances per compound so that not enough information is available to make a complete characterization. Alternatively, proton NMR spectra are difficult to deal with since essentially all of the molecules present in typical samples such as tissue extracts have multiple proton resonances. During the past year we have worked to extend a technique which we initially developed for the characterization of phosphorous metabolites to the analysis of fluorinated compounds. This approach basically involves a combination of INEPT polarization transfer which is used to excite only those protons coupled to fluorine, with a relayed polarization TOCSY experiment to excite the other protons in the molecule. Initial studies have focused on the application of this method to a determination of the metabolites of fluorinated glucose. A second series of studies has been carried out to utilize fluorinated glucose as a probe of glucose transport in erythrocytes. Recent perfused heart studies indicated that several adenosine receptor antagonists were apparently interfering with glucose transport. Studies of the effects of several of these antagonists on the transport of fluorinated glucose across erythrocyte membranes confirm this conclusion.